File POSIX API

Collaboration diagram for File POSIX API:

Functions
int	open (const char *file, int flags,...)
int	creat (const char *path, mode_t mode)
int	close (int fd)
ssize_t	read (int fd, void *buf, size_t len)
ssize_t	write (int fd, const void *buf, size_t len)
off_t	lseek (int fd, off_t offset, int whence)
int	rename (const char *old_file, const char *new_file)
int	unlink (const char *pathname)
int	stat (const char *file, struct stat *buf)
int	fstat (int fildes, struct stat *buf)
int	fsync (int fildes)
int	fcntl (int fildes, int cmd,...)
int	ioctl (int fildes, int cmd,...)
int	ftruncate (int fd, off_t length)
int	statfs (const char *path, struct statfs *buf)
int	fstatfs (int fildes, struct statfs *buf)
int	mkdir (const char *path, mode_t mode)
int	rmdir (const char *pathname)
DIR *	opendir (const char *name)
struct dirent *	readdir (DIR *d)
long	telldir (DIR *d)
void	seekdir (DIR *d, long offset)
void	rewinddir (DIR *d)
int	closedir (DIR *d)
int	access (const char *path, int amode)
void	setcwd (char *buf)
char *	getcwd (char *buf, size_t size)
ssize_t	pread (int fd, void *buf, size_t len, off_t offset)
ssize_t	pwrite (int fd, const void *buf, size_t len, off_t offset)

Detailed Description

Function Documentation

open()

int open	(	const char *	file,
		int	flags,
			...
	)

this function is a POSIX compliant version, which will open a file and return a file descriptor according specified flags.

Parameters

file	the path name of file.
flags	the file open flags.

Returns

the non-negative integer on successful open, others for failed.

creat()

int creat	(	const char *	path,
		mode_t	mode
	)

this function is a POSIX compliant version, which will create a new file or rewrite an existing one

Parameters

path	the path name of file.
mode	the file permission bits to be used in creating the file (not used, can be 0)

Returns

the non-negative integer on successful open, others for failed.

close()

int close

(

int

fd

)

this function is a POSIX compliant version, which will close the open file descriptor.

Parameters

fd	the file descriptor.

Returns

0 on successful, -1 on failed.

read()

ssize_t read	(	int	fd,
		void *	buf,
		size_t	len
	)

this function is a POSIX compliant version, which will read specified data buffer length for an open file descriptor.

Parameters

fd	the file descriptor.
buf	the buffer to save the read data.
len	the maximal length of data buffer

Returns

the actual read data buffer length. If the returned value is 0, it may be reach the end of file, please check errno.

write()

ssize_t write	(	int	fd,
		const void *	buf,
		size_t	len
	)

this function is a POSIX compliant version, which will write specified data buffer length for an open file descriptor.

Parameters

fd	the file descriptor
buf	the data buffer to be written.
len	the data buffer length.

Returns

the actual written data buffer length.

lseek()

off_t lseek	(	int	fd,
		off_t	offset,
		int	whence
	)

this function is a POSIX compliant version, which will seek the offset for an open file descriptor.

Parameters

fd	the file descriptor.
offset	the offset to be seeked.
whence	the directory of seek.

Returns

the current read/write position in the file, or -1 on failed.

rename()

int rename	(	const char *	old_file,
		const char *	new_file
	)

this function is a POSIX compliant version, which will rename old file name to new file name.

Parameters

old_file	the old file name.
new_file	the new file name.

Returns

0 on successful, -1 on failed.

note: the old and new file name must be belong to a same file system.

unlink()

int unlink

(

const char *

pathname

)

this function is a POSIX compliant version, which will unlink (remove) a specified path file from file system.

Parameters

pathname

the specified path name to be unlinked.

Returns

0 on successful, -1 on failed.

stat()

int stat	(	const char *	file,
		struct stat *	buf
	)

this function is a POSIX compliant version, which will get file information.

Parameters

file	the file name
buf	the data buffer to save stat description.

Returns

0 on successful, -1 on failed.

fstat()

int fstat	(	int	fildes,
		struct stat *	buf
	)

this function is a POSIX compliant version, which will get file status.

Parameters

fildes	the file description
buf	the data buffer to save stat description.

Returns

0 on successful, -1 on failed.

fsync()

int fsync

(

int

fildes

)

this function is a POSIX compliant version, which shall request that all data for the open file descriptor named by fildes is to be transferred to the storage device associated with the file described by fildes.

Parameters

fildes

the file description

Returns

0 on successful completion. Otherwise, -1 shall be returned and errno set to indicate the error.

fcntl()

int fcntl	(	int	fildes,
		int	cmd,
			...
	)

this function is a POSIX compliant version, which shall perform a variety of control functions on devices.

Parameters

fildes	the file description
cmd	the specified command
...	represents the additional information that is needed by this specific device to perform the requested function.

Returns

0 on successful completion. Otherwise, -1 shall be returned and errno set to indicate the error.

ioctl()

int ioctl	(	int	fildes,
		int	cmd,
			...
	)

this function is a POSIX compliant version, which shall perform a variety of control functions on devices.

Parameters

fildes	the file description
cmd	the specified command
...	represents the additional information that is needed by this specific device to perform the requested function.

Returns

0 on successful completion. Otherwise, -1 shall be returned and errno set to indicate the error.

ftruncate()

int ftruncate	(	int	fd,
		off_t	length
	)

this function is a POSIX compliant version, which cause the regular file referenced by fd to be truncated to a size of precisely length bytes.

Parameters

fd	the file descriptor.
length	the length to be truncated.

Returns

Upon successful completion, ftruncate() shall return 0; otherwise, -1 shall be returned and errno set to indicate the error.

statfs()

int statfs	(	const char *	path,
		struct statfs *	buf
	)

this function is a POSIX compliant version, which will return the information about a mounted file system.

Parameters

path	the path which mounted file system.
buf	the buffer to save the returned information.

Returns

0 on successful, others on failed.

fstatfs()

int fstatfs	(	int	fildes,
		struct statfs *	buf
	)

this function is a POSIX compliant version, which will return the information about a mounted file system.

Parameters

fildes	the file description.
buf	the buffer to save the returned information.

Returns

0 on successful, others on failed.

mkdir()

int mkdir	(	const char *	path,
		mode_t	mode
	)

this function is a POSIX compliant version, which will make a directory

Parameters

path	the directory path to be made.
mode

Returns

0 on successful, others on failed.

rmdir()

int rmdir

(

const char *

pathname

)

this function is a POSIX compliant version, which will remove a directory.

Parameters

pathname

the path name to be removed.

Returns

0 on successful, others on failed.

opendir()

DIR* opendir

(

const char *

name

)

this function is a POSIX compliant version, which will open a directory.

Parameters

name	the path name to be open.

Returns

the DIR pointer of directory, NULL on open directory failed.

readdir()

struct dirent* readdir

(

DIR *

d

)

this function is a POSIX compliant version, which will return a pointer to a dirent structure representing the next directory entry in the directory stream.

Parameters

d	the directory stream pointer.

Returns

the next directory entry, NULL on the end of directory or failed.

telldir()

long telldir

(

DIR *

d

)

this function is a POSIX compliant version, which will return current location in directory stream.

Parameters

d	the directory stream pointer.

Returns

the current location in directory stream.

seekdir()

void seekdir	(	DIR *	d,
		long	offset
	)

this function is a POSIX compliant version, which will set position of next directory structure in the directory stream.

Parameters

d	the directory stream.
offset	the offset in directory stream.

rewinddir()

void rewinddir

(

DIR *

d

)

this function is a POSIX compliant version, which will reset directory stream.

Parameters

d	the directory stream.

closedir()

int closedir

(

DIR *

d

)

this function is a POSIX compliant version, which will close a directory stream.

Parameters

d	the directory stream.

Returns

0 on successful, -1 on failed.

access()

int access	(	const char *	path,
		int	amode
	)

this function is a POSIX compliant version, which shall check the file named by the pathname pointed to by the path argument for accessibility according to the bit pattern contained in amode.

Parameters

path	the specified file/dir path.
amode	the value is either the bitwise-inclusive OR of the access permissions to be checked (R_OK, W_OK, X_OK) or the existence test (F_OK).

setcwd()

void setcwd

(

char *

buf

)

this function is a POSIX compliant version, which will set current working directory.

Parameters

buf	the current directory.

getcwd()

char* getcwd	(	char *	buf,
		size_t	size
	)

this function is a POSIX compliant version, which will return current working directory.

Parameters

buf	the returned current directory.
size	the buffer size.

Returns

the returned current directory.

pread()

ssize_t pread	(	int	fd,
		void *	buf,
		size_t	len,
		off_t	offset
	)

this function is a POSIX compliant version, which will read specified data buffer length for an open file descriptor.

Parameters

fd	the file descriptor.
buf	the buffer to save the read data.
len	the maximal length of data buffer
offset	the file pos

Returns

the actual read data buffer length. If the returned value is 0, it may be reach the end of file, please check errno.

pwrite()

ssize_t pwrite	(	int	fd,
		const void *	buf,
		size_t	len,
		off_t	offset
	)

this function is a POSIX compliant version, which will write specified data buffer length for an open file descriptor.

Parameters

fd	the file descriptor
buf	the data buffer to be written.
len	the data buffer length.
offset	the file pos

Returns

the actual written data buffer length.